morphophonemics

The changes in pronunciation undergone by allomorphs of morphemes as they are modified by neighboring sounds, as the plural allomorphs in cat-s, dog-s, box-es, or as they are modified for grammatical reasons in the course of inflection or derivation, as house versus to house and housing.

The study of the morphophonemics of a language.

the study of the phonological realization of the allomorphs of the morphemes of a language